How to Build a Shed Foundation

Earlier this year, a Twitter user shared that her brother was going to live in a shed for $220 a week, excluding expenses. Some people found it "adventurous", but the majority found it depressing to pay $200 for a shed that would not even take 30 seconds to have all corners explored. While we can't solve the New Zealand rental crisis right now, a more creative solution is building a shed foundation.

From do-it-yourself outbuildings to office sheds and living spaces, the popularity of custom wooden sheds has skyrocketed over the past decades. The secret to the fantastic sheds you see everywhere is a shed foundation to support them. Building a shed pier foundation sounds challenging, but here's the key: channel your inner Handy Manny and let us guide you.

The concept of having a great foundation can be applied to everything, including sheds. Your shed's foundation has a significant role in whether it succeeds or fails. So, the most critical step is building a durable shed foundation.

On-Grade Foundations or Frost-Proof Foundations?

While there are several types of shed foundations, they can be divided into two categories: on-grade and frost-proof.

  • On-Grade Foundations - this is also called a floating foundation. This style makes the foundation sit directly on the ground. One advantage is that they are quick and simple to construct. For this kind of foundation, digging holes and pouring concrete are unnecessary. On-grade foundations are adequate for the majority of small to medium-sized sheds.

         One option to build this foundation is a concrete slab with sill plates on top, and another option is masonry blocks set on four inches of gravel.

  • Frost-Proof Foundations - frost-proof foundations are more challenging to construct than on-grade ones, but they are significantly stronger and more durable. Consequently, frost-proof foundations are frequently referred to as permanent foundations. Although this foundation can be constructed almost anywhere, it performs best in regions with colder climates and frost heave. For bigger sheds, frost-proof foundations are ideal—and frequently required by regulation.

         The footers are set below the frost line for this foundation to prevent shifting during freezing temperatures. You can use concrete tube forms on gravel with post-base brackets on top.

Build Your Shed Foundation

Now that you have determined which option works best with your space, you can start building the shed foundation.

Step 1: Choose a spot for your shed that's level and doesn't accumulate water. You should have 3 feet of clearance (4 feet for larger sheds) around the perimeter from the fences and structures. This gives you space to construct your shed.

Step 2: Mark the area with mason lines and batter boards. Mason lines and batter boards are used to mark the posts that support the runners' perimeter.

Step 3: You'll need someone to help you square the area. To do so, measure 3 feet along one string and 4 feet along the adjacent string. There should be a 5-feet distance between the two points. Adjust the string and batter boards as needed. Make sure to check the corners.

Step 4: The post holes should be about 4 feet apart. Use mason lines to mark these points. The intersections of the strong will indicate the locations of a post corner. Use the 3:4:5* method to make sure you have a perfectly square corner.

*The 3:4:5 measurement ratio - a 3-foot length on your straight line, a 4-foot length on your perpendicular line, and a 5-foot length across.

Step 5: Create post holes with a diameter of 12 inches and a depth of 12 inches below the frost line. 4 to 6 inches of gravel should be poured into the hole, compacted, and then concrete should be added while mixing according to the manufacturer's instructions. Use the marks on the batter boards to put the mason line back where it belongs if you move it.

Consult with local building code officials to know the frost line depth in your area.

Step 6: Set a post on the footer once the concrete has cured. Make sure the post is straight and upright before adding concrete to the sides and covering it with dirt. To keep each post in place while the concrete cures, brace it. You will want to use treated lumber rated for ground contact for the posts and runners and fasteners, and hardware labelled for treated lumber when assembling the shed foundation blocks and attaching the floor frame.

Step 7: Determine the height you want your shed floor to be and mark one post. Using the marks as a guide, cut the posts with a saw. Remember to wear a dust mask and safety glasses when working with treated lumber.

Step 8: Attach post base brackets and treat 4-inch-by-4-inch runners.

Step 9: According to the instructions for your shed, construct the floor frame using treated 2-by-4s and nails. Note that some shed floor frames use 2-by-6s.

Step 10: Place the frame on the 4-by-4s with an overhang at the ends, and secure one side with a screw to each 4-by-4.

Step 11: You can check the square by measuring the frame's diagonals. Measure between two opposite corners and then between the remaining corners. The measurements need to be equivalent. Make any necessary changes, then fasten the opposite frame side to the 4-by-4s. Next, secure the frame with screws at each location where it meets the 4-by-4s.

Step 12: Place a plywood floor panel flush with the corners at the corner of the frame. After fastening the short edge, repeat the square check on the frame. Make any last-minute adjustments. Install the remaining plywood with nails. Check for level before attaching the additional floor panels per the instructions. Your shed's foundation is prepared.

Shed Foundation Comparison

No matter what shed foundation you like, they all have advantages and disadvantages. There are many factors to consider when choosing the right shed type for your location. You should consider the type of shed you want to build, the landscape of the area you will be working in, and what the weather is like in your area.

Here are some more factors to consider:

  • Shed type
  • Is it economical?
  • Easy to move
  • Waterproof
  • Is it good for slopes?
  • Great support
  • Suitable for cars

Consider Everything Before Building Your Shed

It's exciting to take on building a shed as a summer project, but make sure you have considered everything else before you buy your materials. Getting the measurements right is as vital as checking your local building codes. Check with your chamber of commerce to know what regulations you need to follow. These building codes may affect the location of your shed, its design, and its construction. So, check your local building codes to ensure you follow the rules.

You will also want to decide on the function of your shed, as this will affect its location. Regarding function and location, go around the site and look for any problem that may arise during your construction to prevent future complications. For example, if your yard is dense with trees, consider if falling leaves or branches could damage the roof or foundation. Another thing to bear in mind is that tree roots can occasionally cause issues. Consider removing a tree if there needs to be clear space for the shed. Additionally, check that your construction site is flat and has sufficient drainage. You don't want any water near your shed due to poor drainage.

Consider adding elements to your shed that will enhance its functionality. Additionally, add exterior accents to your shed, including beautiful trim, shutters, and a lovely paint job, to make it seem even better from the outside. It's wonderful to look for shed plans that offer elements that make your shed a little bit better, even while the fun aspects aren't the most crucial.


With everything that needs to be assessed and evaluated, building a shed foundation can sound intimidating. But just like anything else, you'll swoon over the final product and be glad you decided to take on the challenge. Keep in mind that this is not an overnight project, so take your sweet time with the whole process.

The Wooden Shed Company offers a variety of backyard or garden shed designs to build your home office shed. We can also customise based on your unique space requirements.


Related Reads:


Contact Us

Phone: 027 441 4010


Address: 875 German Road, Starvation Hill 7495, New Zealand